Frequency dependence of coercivity in nickel and Co-Fe-B thin film for DC to 100 kHz region

To investigate the magnetization process in the intermediate frequency region, the frequency dependences of coercivities in Ni and Co-Fe-B thin films were determined by anisotropic magnetoresistance measurements up to similar to 160 kHz. In the low-frequency region (<5 kHz) the coercivity of Co-Fe-B was lower than that of Ni. However, the increasing rate of the coercivity in Ni was lower than that in Co-Fe-B. Consequently, above 19 kHz, the coercivity of Ni was lower than one of Co-Fe-B. Considering the basic material properties, better soft magnetic properties of Ni compared with Co-Fe-B should arise from the higher Walker breakdown field. This difference was mainly due to the Gilbert damping constant.